1. Field of the Invention
The present invention is directed to a system and device for automatically controlling lights or appliances in a room. More particularly, the present invention is directed to a system and device which keeps track of the number of persons who have entered and exited from a room, and which turns an electric light or appliance off only when the number of persons who have exited equals the number of persons who have entered.
2. Brief Description of the Prior Art
Various types of electric timing devices are used in the art for controlling lights in households. The timers may, for example, be set to switch a light on and off at predetermined times every day.
Various types of sensors and associated electric and logic circuits are also known in the art to be used as burglar alarms, that is, for the detection of unauthorized entry by persons into an enclosure. The senors for burglar alarms work on a wide variety of physical principles. For example, some burglar alarms utilize photoelectric sensors (electric eyes) while others use motion sensors or infrared detectors, and still others use pressure sensors mounted into floors, to detect unauthorized entry.
In spite of the relative sophistication of the prior art technology for detecting unauthorized entry into a building or enclosure, as far as the present inventor knows there are no simple and inexpensive devices in the prior art designed for controlling a light or electric appliance in a room or enclosure simply on the basis whether or not the number of persons who have entered the room equals the number of persons who have left a room. The present invention provides such a device.